The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Harvested grain may be dried and stored for extended lengths of time in grain silos or grain bins, because of fluctuating market conditions. Additionally, moist grain may be held in bins and then heated with forced air to extract the moisture. Grain bins typically include a cylindrical body and a conical roof. The body can be a peripheral wall typically comprised of bolted or welded, smooth or corrugated wall panels. The conical roof can have a 20-40 degree slope, and is typically comprised of pie-shaped or radial roof panels with integrated ribs or stiffeners along the two long sides of the panels. These ribs provide strength and stiffness to the panels, allowing them to span between the storage structure's walls and a fill hole collar or to intermediate structural elements located beneath or above the panels.
Grain is typically loaded into these structures through a fill hole at the top of the roof and unloaded via an under floor auger system accessed through operable floor sumps. Because grain may be stored for a relatively long time, methods for preserving the condition of the grain against moisture, temperature, and insects are used. To aid in preserving grain against moisture, grain storage structures typically employ an under floor aeration system, utilizing fans which distribute air horizontally through a plenum space, vertically through a perforated floor into the grain mass, and out through vents located in the roof of the structure. For this function, the roof vents provide a critical outlet for the created pressure, the absence of which could result in excessive stress and damage to the roof structure and containment of moisture limiting the effectiveness of the grain bin. To aid in preserving grain against the negative effects of high ambient air temperatures that tend to occur at the inside peak of the roof, roof vents are again utilized, relieving the build-up of hot air by means of natural convection.
While roof venting is desired and even necessary during some processes of conditioning grain, roof vents can be detrimental in other processes. Grain must also be preserved against insects, which can enter the storage structure as larvae during loading, or as flying insects through vent screens. The typical method to remedy this problem is fumigation of the storage container. This process is performed within the container and requires that the container be reasonably airtight. Roof vents must be sealed in some way prior to fumigating, a process that can take substantial time and often poses some safety risk. In addition to the fumigation process, roof vents also must often be closed during the grain loading process. During grain loading, substantial grain dust is generated which can escape through roof vents and settle on surrounding structures. Many municipalities require that grain storage facilities located within town limits prevent the migration of grain dust during loading.
Typically, roof venting systems include a series of roof panels located at regular radial intervals, with a single hole cut in the flat portion between the integrated ribs, and capped with a metal shroud which allows air to escape while preventing rain or snow from entering into the container. The metal shrouds are comprised of multiple parts and are fastened to the roof panel in the field during the construction of the storage structure. The number and frequency of vented panels varies based on the container's capacity, fan output, climate, and other venting requirements. Because of the size of the vent hole and shroud, the pie shape of the roof panels, and the natural convergence of the integrated ribs towards the top of the container's roof peak, the vent hole in the vented panels is typically located in the end of the panel nearest to the container's wall. This location is not ideal, as the heated air that desires relief by natural convection, is located at the peak of the roof, not the eave.
Existing vents can be expensive and time-consuming to install, can often leak because of difficulties in installation, can trap material, and can lead to rusting around the vents. There is, therefore, a need for improved venting systems for grain bins.